Direct Imaging of Polariton Relaxation Dynamics in TMDC Microcavities
ORAL
Abstract
Transition metal dichalcogenides (TMDCs) have emerged as versatile platforms for exploring exciton-polaritons—quasiparticles formed through strong coupling between excitons and cavity-confined photons—owing to their ease of fabrication, rich excitonic spectra, and exceptional tunability. Their ability to host exotic many-body phases, such as room-temperature Bose-Einstein condensates [1], positions TMDCs as prime systems for studying quantum phenomena and advancing optoelectronic and quantum technologies. However, key processes such as phonon-assisted polariton relaxation—proposed to play a critical role in the formation and stability of coherent quantum states—remain poorly understood, as direct experimental evidence of these processes is still limited.
To address this, we employ ultrafast pump-probe and time-resolved photoluminescence microscopy to directly image the momentum relaxation of polariton populations in tungsten diselenide (WSe2)-based Fabry-Pérot cavities. Most notably, we observe relaxation behavior that is enhanced at higher temperatures and maximized under favorable energetic alignment with dark excitonic states and phonon resonances. Complementing our experimental findings, we employ microscopic theoretical modeling based on semiclassical Boltzmann equations to resolve the full time- and momentum-dependent exciton-polariton dynamics [2]. These insights advance our understanding of relaxation processes in TMDC-based polaritonic systems and lay the groundwork for the controlled engineering of quantum light-matter states.
References
[1] J. Zhao et al., Ultralow threshold polariton condensate in a monolayer semiconductor microcavity at room temperature, Nano Lett. 21, 3331 (2021).
[2] J. M. Fitzgerald et al., Circumventing the polariton bottleneck via dark excitons in 2D semiconductors, Optica 11, 1346 (2024).
To address this, we employ ultrafast pump-probe and time-resolved photoluminescence microscopy to directly image the momentum relaxation of polariton populations in tungsten diselenide (WSe2)-based Fabry-Pérot cavities. Most notably, we observe relaxation behavior that is enhanced at higher temperatures and maximized under favorable energetic alignment with dark excitonic states and phonon resonances. Complementing our experimental findings, we employ microscopic theoretical modeling based on semiclassical Boltzmann equations to resolve the full time- and momentum-dependent exciton-polariton dynamics [2]. These insights advance our understanding of relaxation processes in TMDC-based polaritonic systems and lay the groundwork for the controlled engineering of quantum light-matter states.
References
[1] J. Zhao et al., Ultralow threshold polariton condensate in a monolayer semiconductor microcavity at room temperature, Nano Lett. 21, 3331 (2021).
[2] J. M. Fitzgerald et al., Circumventing the polariton bottleneck via dark excitons in 2D semiconductors, Optica 11, 1346 (2024).
*We acknowledge the support from the US Department of Energy, Office of Basic Energy Sciences through QuPIDC EFRC award DE-DOE-SC0025620
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Presenters
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Minxue Wang
- Purdue University